A feature of Instant Messaging (IM) services is possible instant communication over a network. IM, which emerged not long ago, has become one of the most popular services over the Internet.
Along with high speed development of the mobile communication market, the number of users of mobile phones is increasing rapidly, and integration of IM and mobile communication becomes an inevitable trend. Users have a strong demand for keeping IM online constantly while they are outgoing. For IM providers, applying IM services over the Internet to the mobile communication field will widely broaden revenue sources; and for operators, mobile IM provides an important service leading to improved revenues from data services, an increased Average Revenue Per User (ARPU) value and a reduced loss of users. In this case, precise charging of various IM services deployed over a mobile network becomes a key issue of successful operation of mobile IM services.
With reference to FIG. 1, in a communication charging method existing in the related art, when a text or multimedia message or file is transmitted between IM users, an operator relays and forwards message media contents through an IM server in order to concentratively control or collect media transmission information.
As illustrated in FIG. 1, reference signs 101, 105 and 106 each denote transmission of Message Session Relay Protocol (MSRP) messages, and reference signs 102, 103 and 104 each denote transmission of Session Initiation Protocol (SIP) messages.
In this case, either a Page Mode message transmitted using the SIP MESSAGE protocol or a session based IM message transmitted using the MSRP between the IM users needs to pass through the IM server. The IM server can obtain information in the IM message required for various charges. Charging messages are collected and sent to a charging system so that the charging system can accomplish charging of an IM service.
However, when one-to-one IM communication is conducted between only two IM users, message contents may not pass through the IM server, but instead be transmitted directly between the IM users in order to improve efficiency of media transmission. This transmission approach is referred to as peer-to-peer transmission.
When information is transmitted using the MSRP between two IM users in peer-to-peer communication, MSRP messages are not forwarded through the IM server.
In the solution of the related art, for such a peer-to-peer communication service, only start time and end time of a session can be acquired at an application layer. As a result, precise charging of peer-to-peer communication can not be implemented.
For a service based upon an IP Multimedia Subsystem (IMS), for example, usage of media resources after establishment of a session cannot be obtained by session charging applicable to MRSP communication, so that precision of charging can not be guaranteed and charging and operation of an IM service by an operator may be influenced.